Next problem... this is part of the Voyager print.

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(Richard Blackman) #1

Next problem… this is part of the Voyager print. I have tried about 10 prints of different parts and keep getting this issue where extra loops are being pushed out. These pictures show the worst one front and back.
I have tried temps from 175 to 190 deg (this is PLA), I changed the extrusion multiplier from 1 to .9 in case it was overextruding. I have tried it at different scales, this is 75% but I get the same at 100%.
You can see that I’m not getting any extra ooze or stringing between the uprights, at least that problem is much better.
Again, I appreciate any ideas of what to try next.

(Stephen Baird) #2

Have you tried calibrating you E steps/mm? It looks like some kind of serious over extrusion problem to me.

The easiest way I’ve found to check your calibration is to cut a straw to exactly 100mm, then slit it up the side. Stick that onto your filament and slide it right up against the top of your extruder/hot end mount/whatever is the furthest toward the hot end you can get it and make a mark at the back of the straw.

Then heat everything up and tell the printer to extrude 100mm. If the mark you made on the filament is right up against the top of your extruder/hot end mount/whatever you’re good. If it’s not, make a mark on the filament at the top of the extruder/hot end mount/whatever then back the filament out.

Measure the distance between the two marks, and this will tell you how much over extrusion you had. To fix it, do some math:

Current E steps * (100 / total extrusion length [that’s 100 + distance of over extrusion measured ])

Then feed that newly calculated number into your EEPROM as your E steps/mm value and repeat the test to make sure the number is now right.

(Stephen Baird) #3

The extrusion multiplier is more for handling the different behaviors of plastics than for fixing miscalibrated E steps. If you want to calibrate that, you want to print a single walled cube (the 5mm single walled cube on Thingiverse is nice) then measure the thickness of the wall (near the top, since you get bulging at the bottom for better adhesion usually) and compare that to the wall thickness you have set in your slicer.

So if, for example, you had a set wall thickness of .42 and measured a wall thickness of .47 you’d want to use .9 for an extrusion multiplier (because .42/.47 is, more or less, .9).

Extrusion multiplier is more of a fine calibration, while the E steps/mm is a rough calibration. And that looks to me like an incorrect extruder steps sort of problem.

(Joseph Chiu) #4

Hmmm, my earlier comment seemed to have disappeared. As @Stephen_Baird has also mentioned, you have a very significant over-extrusion problem. I highly suggest, as a quick sanity check, to try reslicing your prints with a deliberately over-stated filament diameter (say by about 15%-20%) and then compare the resulting print.

For that matter, I suggest going back to basics, and print a 100% infill calibration cube. That will be a really fast way to help dial in your extrusion rate.

(Richard Blackman) #5

Thanks guys, that gives me a direction to go. Thanks @Stephen_Baird for the tip about the straw. I did the esteps callibration when I first set this up but it has been a while.
To me it seems weird that in general straight up walls are fine, it starts messing up on the outward curves.
I don’t have any more time to mess with it today but I will go back and recalibrate.
BTW LH was .2 on this print.

(Joseph Chiu) #6

The reason why it’s not so obvious on straight walls is because you are laying down the same shape over and over again – so that it looks like it’s fine, especially if there’s a gap within the perimeter wall that can absorb some of the overextrusion. This is why, in that other post of yours, different scaling can cause the wall to look nice and then wonky – as the thickness of the feature changes, the small gaps that could absorb the errors change, and in some cases, can no longer absorb the over-extrusion.

(Stephen Baird) #7

Yeah, the straight walls in this print also show signs of serious over extrusion. They look sort of puffy, almost like an overstuffed armchair, and you’ve got some squishing out perimeters in there too. Calibrating the extruder should fix this.

(Nick Benik (HackerCEO)) #8

what printer are you using?

(Stephen Jensen) #9

Also say what kind of extruder, nozzle type and size. Have you tried extruder calibration: http://www.ohmeye.com/2013/reprap-extrusion-flow-calibration/ ?

(Richard Blackman) #10

This is a Prusa Mendal, J-Head mk IV .5. Built in March 2012 this is a new problem. I have a little spare time this morning so am going to start by rechecking esteps, then I’ll print a cube and recheck my x,y, z calibration. If that doesn’t help I’ll try the extruder calibration.
Note that these pics taken with my S3 and in good light really show up every defect.

(Richard Blackman) #11

Starting a new thread with a new pic.